The Sewage Sludge thresholds remain just as relevant today as they were when the SGV for lead was current, they're not linked (are they?). The thresholds are derived with regard to effects on grazing livestock rather than humans.
The last time I looked at sewage sludge I saw a proposed new Sludge Directive that reduced acceptable concentrations (Lead came down to 70mg/kg-pH<7 and 100mg/kg-pH>7). You may want to find out whether or not this new Directive made it past committee.
A concentration of 140mg/kg doesn't seem that high, what are the other concentrations and what sort of distribution do they have, being mindful not to include duplicate samples in your stats because then you're not using an unbiased sample population of the whole field.
Comparing against the C4SLs for residential use of 200mg/kg it doesn't appear to present a massive problem unless you're thinking of allotments.
Cheers
Clive Williams
|